Previous work has shown that even mixed metal oxide (MMO) anodes are able to form chlorate and perchlorate when solutions containing Cl- ions are electrolysed in undivided cells. Both chlorate and perchlorate are under suspicion for causing several diseases. For the first time, different research groups systematically studied electrode materials [three MMO anode materials and one boron-doped diamond (BDD) anode material as well as technical cells of four producers] for chlorate and perchlorate formation potential under laboratory- and technical-scale conditions. Natural and artificial water samples were used mostly at room temperature, at current densities between 10 and 571 A m(-2), with the highest being for BDD anodes, and focusing on water samples with chloride contents between 20 mg dm(-3) (0.56 mmol L-1) and 250 mg L-1 (7.04 mmol L-1). Two model water samples were defined to be used as test standards in the future. Only one MMO material showed chlorate formation in the laboratory experiments, whereas in technical cells, in all four cases, chlorate was detected, but perchlorate was not found on MMO anodes. New introduced criteria allow a better risk quantification. According to these criteria, all three cells with MMO anodes are safe when chlorate is limited in drinking water to be below 0.2 mg dm(-3). Taking into consideration the advisory perchlorate concentration level suggested by the U.S.E.P.A., no recommendation can be given for cells with BDD anodes with significant chlorate and perchlorate formation.